Diamonds fluoresce during exposure to ultraviolet light (UV light). Some diamonds normally present blue fluorescence under UV light while a few present yellow fluorescence.
In addition to the property of exhibiting fluorescence, some diamonds phosphoresce. Diamond fluorescence is the phenomenon when diamonds are exposed to UV light and present blue fluorescence at different intensities. Diamonds phosphorescence is the light emission of diamonds after the UV light is turned off.
Since different diamonds present various colors of fluorescence at various intensities, the simplest method for preliminary detection on large quantities of diamonds is exposing them under UV light. If the diamonds fluoresce different colors at different intensities, they are natural diamonds; if, however, the fluorescence emitted by the diamonds presents the same color at the same intensity, it is probably that the diamonds are synthetic diamonds.
In recent years, synthetic diamonds have been mixed into natural diamonds for sell by illegal businessmen. Conventional diamond detection methods are slow for screening large quantities of synthetic diamonds and natural diamonds. Moreover, the equipments and detection methods are normally designed for detecting big size diamonds but of no use when fast screening of melee diamonds (very small diamonds) is in need. Normally, diamond dealers purchase large amount of melee diamonds and thus spend a lot of time on conventional diamond detection without reducing the risk of purchasing synthetic diamonds.